The candidate seeks funding to extend her training in epidemiology in two new directions, namely, human placental biology and mass spectrometry. Learning these laboratory-based methods will move her closer to accomplishing her long-term goals of becoming an independent academic investigator and offering new insights and methods to research on low dose chronic exposures to endocrine disrupting compounds and their role in health disorders that originate in early pregnancy. During the K99 phase, under the primary mentorship of Dr. Susan Fisher, the candidate will receive training in trophoblast (Tb) stem cell biology, state-of-the-art microarray-based methodologies that are used to analyze gene expression at a global level, including bioinformatics approaches for data analysis. Building on the results of her initial postdoctoral research, the candidate theorize that Tbs, the specialized cells that carry out many of the placenta's most important functions, are exposed to phthalates early in pregnancy with adverse consequences on placental development and function. The investigators will test hypotheses regarding clinical outcomes and biological parameters that include molecular, cellular, and morphologic measures of human placental development and function. Specifically, they will conduct experiments to test the hypothesis that cultured human Tb stem cells will show dose-dependent changes in patterns of gene expression when they are exposed to environmentally relevant doses of di-(2-ethylhexyl) phthalate and di-n-butyl phthalate (Aim 1). During the R00 phase, the candidate will test the theory, in a longitudinal study of pregnant women, that placental genes that are differentially expressed as a consequence of phthalate exposure in vitro are similarly regulated, in a dose-dependent manner, in vivo (Aim 2). As part of this aim, the candidate will evaluate the correlation between the conventional dosimeter of prenatal exposure, urinary phthalate metabolite concentrations, and the dose to the target placental tissue. The primary mentor and co-mentors in obstetrics/gynecology, mass spectrometry, biostatistics, and epidemiology will guide the process whereby the candidate learn the methods that are required to accomplish the goals set forth in this proposal. At the conclusion of this training program the candidate will have developed new methodologies and tools that she and other investigators can use to ask more directed questions about the consequences of phthalate exposures during pregnancy in terms of alterations in placental function and consequently, human development. This work is important because phthalates, which can disrupt cell and tissue differentiation, are well established as reproductive and developmental toxicants in rodents;yet the relevance of these finding to humans is not well understood. With biomarkers specific to phthalate-induced placental damage, it will become possible to identify high-risk pregnancies and provide opportunities for prevention, at the population level, and possibly intervention at the level of health care delivery systems to improve placental and fetal outcomes. Public Health Relevance: The goal of this project is to prepare Dr. Jennifer Adibi to transition to a position as an independent academic investigator in environmental health sciences focusing on the consequences of phthalate exposures during human pregnancy. She will conduct experiments using in vitro and in vivo models to test the hypothesis that this toxicant disrupts trophoblast differentiation, and therefore placental development and function, thereby compromising human development in-utero.